Add missing @Nullable annotations on parameters

Issue: SPR-15540

spring-aop/src/main/java/org/springframework/aop/TrueMethodMatcher.java

@@ -19,6 +19,8 @@ package org.springframework.aop;
 import java.io.Serializable;
 import java.lang.reflect.Method;
 
+import org.springframework.lang.Nullable;
+
 /**
  * Canonical MethodMatcher instance that matches all methods.
  *
@@ -43,12 +45,12 @@ class TrueMethodMatcher implements MethodMatcher, Serializable {
 	}
 
 	@Override
-	public boolean matches(Method method, Class<?> targetClass) {
+	public boolean matches(Method method, @Nullable Class<?> targetClass) {
 		return true;
 	}
 
 	@Override
-	public boolean matches(Method method, Class<?> targetClass, Object... args) {
+	public boolean matches(Method method, @Nullable Class<?> targetClass, Object... args) {
 		// Should never be invoked as isRuntime returns false.
 		throw new UnsupportedOperationException();
 	}

spring-aop/src/main/java/org/springframework/aop/aspectj/AbstractAspectJAdvice.java

@@ -698,7 +698,7 @@ public abstract class AbstractAspectJAdvice implements Advice, AspectJPrecedence
 		}
 
 		@Override
-		public boolean matches(Method method, Class<?> targetClass) {
+		public boolean matches(Method method, @Nullable Class<?> targetClass) {
 			return !this.adviceMethod.equals(method);
 		}
 

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJAfterReturningAdvice.java

@@ -61,7 +61,7 @@ public class AspectJAfterReturningAdvice extends AbstractAspectJAdvice
 	}
 
 	@Override
-	public void afterReturning(Object returnValue, Method method, Object[] args, Object target) throws Throwable {
+	public void afterReturning(@Nullable Object returnValue, Method method, Object[] args, @Nullable Object target) throws Throwable {
 		if (shouldInvokeOnReturnValueOf(method, returnValue)) {
 			invokeAdviceMethod(getJoinPointMatch(), returnValue, null);
 		}

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJExpressionPointcut.java

@@ -277,7 +277,7 @@ public class AspectJExpressionPointcut extends AbstractExpressionPointcut
 	}
 
 	@Override
-	public boolean matches(Method method, Class<?> targetClass, boolean beanHasIntroductions) {
+	public boolean matches(Method method, @Nullable Class<?> targetClass, boolean beanHasIntroductions) {
 		checkReadyToMatch();
 		Method targetMethod = AopUtils.getMostSpecificMethod(method, targetClass);
 		ShadowMatch shadowMatch = getShadowMatch(targetMethod, method);
@@ -306,7 +306,7 @@ public class AspectJExpressionPointcut extends AbstractExpressionPointcut
 	}
 
 	@Override
-	public boolean matches(Method method, Class<?> targetClass) {
+	public boolean matches(Method method, @Nullable Class<?> targetClass) {
 		return matches(method, targetClass, false);
 	}
 
@@ -317,7 +317,7 @@ public class AspectJExpressionPointcut extends AbstractExpressionPointcut
 	}
 
 	@Override
-	public boolean matches(Method method, Class<?> targetClass, Object... args) {
+	public boolean matches(Method method, @Nullable Class<?> targetClass, Object... args) {
 		checkReadyToMatch();
 		ShadowMatch shadowMatch = getShadowMatch(AopUtils.getMostSpecificMethod(method, targetClass), method);
 		ShadowMatch originalShadowMatch = getShadowMatch(method, method);

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJMethodBeforeAdvice.java

@@ -20,6 +20,7 @@ import java.io.Serializable;
 import java.lang.reflect.Method;
 
 import org.springframework.aop.MethodBeforeAdvice;
+import org.springframework.lang.Nullable;
 
 /**
  * Spring AOP advice that wraps an AspectJ before method.
@@ -39,7 +40,7 @@ public class AspectJMethodBeforeAdvice extends AbstractAspectJAdvice implements
 
 
 	@Override
-	public void before(Method method, Object[] args, Object target) throws Throwable {
+	public void before(Method method, Object[] args, @Nullable Object target) throws Throwable {
 		invokeAdviceMethod(getJoinPointMatch(), null, null);
 	}
 

spring-aop/src/main/java/org/springframework/aop/aspectj/annotation/InstantiationModelAwarePointcutAdvisorImpl.java

@@ -31,6 +31,7 @@ import org.springframework.aop.aspectj.InstantiationModelAwarePointcutAdvisor;
 import org.springframework.aop.aspectj.annotation.AbstractAspectJAdvisorFactory.AspectJAnnotation;
 import org.springframework.aop.support.DynamicMethodMatcherPointcut;
 import org.springframework.aop.support.Pointcuts;
+import org.springframework.lang.Nullable;
 
 /**
  * Internal implementation of AspectJPointcutAdvisor.
@@ -274,14 +275,14 @@ class InstantiationModelAwarePointcutAdvisorImpl
 		}
 
 		@Override
-		public boolean matches(Method method, Class<?> targetClass) {
+		public boolean matches(Method method, @Nullable Class<?> targetClass) {
 			// We're either instantiated and matching on declared pointcut, or uninstantiated matching on either pointcut
 			return (isAspectMaterialized() && this.declaredPointcut.matches(method, targetClass)) ||
 					this.preInstantiationPointcut.getMethodMatcher().matches(method, targetClass);
 		}
 
 		@Override
-		public boolean matches(Method method, Class<?> targetClass, Object... args) {
+		public boolean matches(Method method, @Nullable Class<?> targetClass, Object... args) {
 			// This can match only on declared pointcut.
 			return (isAspectMaterialized() && this.declaredPointcut.matches(method, targetClass));
 		}

spring-aop/src/main/java/org/springframework/aop/aspectj/annotation/ReflectiveAspectJAdvisorFactory.java

@@ -315,7 +315,7 @@ public class ReflectiveAspectJAdvisorFactory extends AbstractAspectJAdvisorFacto
 		public SyntheticInstantiationAdvisor(final MetadataAwareAspectInstanceFactory aif) {
 			super(aif.getAspectMetadata().getPerClausePointcut(), new MethodBeforeAdvice() {
 				@Override
-				public void before(Method method, Object[] args, Object target) {
+				public void before(Method method, Object[] args, @Nullable Object target) {
 					// Simply instantiate the aspect
 					aif.getAspectInstance();
 				}

spring-aop/src/main/java/org/springframework/aop/framework/AbstractSingletonProxyFactoryBean.java

@@ -24,6 +24,7 @@ import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.beans.factory.FactoryBean;
 import org.springframework.beans.factory.FactoryBeanNotInitializedException;
 import org.springframework.beans.factory.InitializingBean;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 
 /**
@@ -123,7 +124,7 @@ public abstract class AbstractSingletonProxyFactoryBean extends ProxyConfig
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		if (this.proxyClassLoader == null) {
 			this.proxyClassLoader = classLoader;
 		}

spring-aop/src/main/java/org/springframework/aop/framework/CglibAopProxy.java

@@ -153,7 +153,7 @@ class CglibAopProxy implements AopProxy, Serializable {
 	}
 
 	@Override
-	public Object getProxy(ClassLoader classLoader) {
+	public Object getProxy(@Nullable ClassLoader classLoader) {
 		if (logger.isDebugEnabled()) {
 			logger.debug("Creating CGLIB proxy: target source is " + this.advised.getTargetSource());
 		}

spring-aop/src/main/java/org/springframework/aop/framework/DefaultAdvisorChainFactory.java

@@ -32,6 +32,7 @@ import org.springframework.aop.PointcutAdvisor;
 import org.springframework.aop.framework.adapter.AdvisorAdapterRegistry;
 import org.springframework.aop.framework.adapter.GlobalAdvisorAdapterRegistry;
 import org.springframework.aop.support.MethodMatchers;
+import org.springframework.lang.Nullable;
 
 /**
  * A simple but definitive way of working out an advice chain for a Method,
@@ -48,7 +49,7 @@ public class DefaultAdvisorChainFactory implements AdvisorChainFactory, Serializ
 
 	@Override
 	public List<Object> getInterceptorsAndDynamicInterceptionAdvice(
-			Advised config, Method method, Class<?> targetClass) {
+			Advised config, Method method, @Nullable Class<?> targetClass) {
 
 		// This is somewhat tricky... We have to process introductions first,
 		// but we need to preserve order in the ultimate list.

spring-aop/src/main/java/org/springframework/aop/framework/JdkDynamicAopProxy.java

@@ -31,6 +31,7 @@ import org.springframework.aop.RawTargetAccess;
 import org.springframework.aop.TargetSource;
 import org.springframework.aop.support.AopUtils;
 import org.springframework.core.DecoratingProxy;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 
@@ -113,7 +114,7 @@ final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializa
 	}
 
 	@Override
-	public Object getProxy(ClassLoader classLoader) {
+	public Object getProxy(@Nullable ClassLoader classLoader) {
 		if (logger.isDebugEnabled()) {
 			logger.debug("Creating JDK dynamic proxy: target source is " + this.advised.getTargetSource());
 		}

spring-aop/src/main/java/org/springframework/aop/framework/ProxyFactoryBean.java

@@ -45,6 +45,7 @@ import org.springframework.beans.factory.FactoryBean;
 import org.springframework.beans.factory.FactoryBeanNotInitializedException;
 import org.springframework.beans.factory.ListableBeanFactory;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
 
@@ -213,13 +214,13 @@ public class ProxyFactoryBean extends ProxyCreatorSupport
 	 * containing BeanFactory for loading all bean classes. This can be
 	 * overridden here for specific proxies.
 	 */
-	public void setProxyClassLoader(ClassLoader classLoader) {
+	public void setProxyClassLoader(@Nullable ClassLoader classLoader) {
 		this.proxyClassLoader = classLoader;
 		this.classLoaderConfigured = (classLoader != null);
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		if (!this.classLoaderConfigured) {
 			this.proxyClassLoader = classLoader;
 		}

spring-aop/src/main/java/org/springframework/aop/framework/ProxyProcessorSupport.java

@@ -21,6 +21,7 @@ import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.core.Ordered;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
 
@@ -81,7 +82,7 @@ public class ProxyProcessorSupport extends ProxyConfig implements Ordered, BeanC
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		if (!this.classLoaderConfigured) {
 			this.proxyClassLoader = classLoader;
 		}

spring-aop/src/main/java/org/springframework/aop/framework/ReflectiveMethodInvocation.java

@@ -28,6 +28,7 @@ import org.aopalliance.intercept.MethodInvocation;
 import org.springframework.aop.ProxyMethodInvocation;
 import org.springframework.aop.support.AopUtils;
 import org.springframework.core.BridgeMethodResolver;
+import org.springframework.lang.Nullable;
 
 /**
  * Spring's implementation of the AOP Alliance
@@ -240,7 +241,7 @@ public class ReflectiveMethodInvocation implements ProxyMethodInvocation, Clonea
 
 
 	@Override
-	public void setUserAttribute(String key, Object value) {
+	public void setUserAttribute(String key, @Nullable Object value) {
 		if (value != null) {
 			if (this.userAttributes == null) {
 				this.userAttributes = new HashMap<>();

spring-aop/src/main/java/org/springframework/aop/framework/autoproxy/AbstractAdvisorAutoProxyCreator.java

@@ -24,6 +24,7 @@ import org.springframework.aop.support.AopUtils;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
+import org.springframework.lang.Nullable;
 
 /**
  * Generic auto proxy creator that builds AOP proxies for specific beans
@@ -66,7 +67,8 @@ public abstract class AbstractAdvisorAutoProxyCreator extends AbstractAutoProxyC
 
 
 	@Override
-	protected Object[] getAdvicesAndAdvisorsForBean(Class<?> beanClass, String beanName, TargetSource targetSource) {
+	@Nullable
+	protected Object[] getAdvicesAndAdvisorsForBean(Class<?> beanClass, String beanName, @Nullable TargetSource targetSource) {
 		List<Advisor> advisors = findEligibleAdvisors(beanClass, beanName);
 		if (advisors.isEmpty()) {
 			return DO_NOT_PROXY;

spring-aop/src/main/java/org/springframework/aop/framework/autoproxy/BeanNameAutoProxyCreator.java

@@ -22,6 +22,7 @@ import java.util.List;
 import org.springframework.aop.TargetSource;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.FactoryBean;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.PatternMatchUtils;
 import org.springframework.util.StringUtils;
@@ -73,7 +74,8 @@ public class BeanNameAutoProxyCreator extends AbstractAutoProxyCreator {
 	 * Identify as bean to proxy if the bean name is in the configured list of names.
 	 */
 	@Override
-	protected Object[] getAdvicesAndAdvisorsForBean(Class<?> beanClass, String beanName, TargetSource targetSource) {
+	@Nullable
+	protected Object[] getAdvicesAndAdvisorsForBean(Class<?> beanClass, String beanName, @Nullable TargetSource targetSource) {
 		if (this.beanNames != null) {
 			for (String mappedName : this.beanNames) {
 				if (FactoryBean.class.isAssignableFrom(beanClass)) {

spring-aop/src/main/java/org/springframework/aop/support/AbstractRegexpMethodPointcut.java

@@ -20,6 +20,7 @@ import java.io.Serializable;
 import java.lang.reflect.Method;
 import java.util.Arrays;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
@@ -129,7 +130,7 @@ public abstract class AbstractRegexpMethodPointcut extends StaticMethodMatcherPo
 	 * plus the name of the method.
 	 */
 	@Override
-	public boolean matches(Method method, Class<?> targetClass) {
+	public boolean matches(Method method, @Nullable Class<?> targetClass) {
 		return ((targetClass != null && matchesPattern(ClassUtils.getQualifiedMethodName(method, targetClass))) ||
 				matchesPattern(ClassUtils.getQualifiedMethodName(method)));
 	}

spring-aop/src/main/java/org/springframework/aop/support/ControlFlowPointcut.java

@@ -80,7 +80,7 @@ public class ControlFlowPointcut implements Pointcut, ClassFilter, MethodMatcher
 	 * some candidate classes.
 	 */
 	@Override
-	public boolean matches(Method method, Class<?> targetClass) {
+	public boolean matches(Method method, @Nullable Class<?> targetClass) {
 		return true;
 	}
 
@@ -90,7 +90,7 @@ public class ControlFlowPointcut implements Pointcut, ClassFilter, MethodMatcher
 	}
 
 	@Override
-	public boolean matches(Method method, Class<?> targetClass, Object... args) {
+	public boolean matches(Method method, @Nullable Class<?> targetClass, Object... args) {
 		this.evaluations++;
 
 		for (StackTraceElement element : new Throwable().getStackTrace()) {

spring-aop/src/main/java/org/springframework/aop/support/DynamicMethodMatcher.java

@@ -19,6 +19,7 @@ package org.springframework.aop.support;
 import java.lang.reflect.Method;
 
 import org.springframework.aop.MethodMatcher;
+import org.springframework.lang.Nullable;
 
 /**
  * Convenient abstract superclass for dynamic method matchers,
@@ -36,7 +37,7 @@ public abstract class DynamicMethodMatcher implements MethodMatcher {
 	 * always returns true.
 	 */
 	@Override
-	public boolean matches(Method method, Class<?> targetClass) {
+	public boolean matches(Method method, @Nullable Class<?> targetClass) {
 		return true;
 	}
 

spring-aop/src/main/java/org/springframework/aop/support/MethodMatchers.java

@@ -114,13 +114,13 @@ public abstract class MethodMatchers {
 		}
 
 		@Override
-		public boolean matches(Method method, Class<?> targetClass, boolean hasIntroductions) {
+		public boolean matches(Method method, @Nullable Class<?> targetClass, boolean hasIntroductions) {
 			return (matchesClass1(targetClass) && MethodMatchers.matches(this.mm1, method, targetClass, hasIntroductions)) ||
 					(matchesClass2(targetClass) && MethodMatchers.matches(this.mm2, method, targetClass, hasIntroductions));
 		}
 
 		@Override
-		public boolean matches(Method method, Class<?> targetClass) {
+		public boolean matches(Method method, @Nullable Class<?> targetClass) {
 			return (matchesClass1(targetClass) && this.mm1.matches(method, targetClass)) ||
 					(matchesClass2(targetClass) && this.mm2.matches(method, targetClass));
 		}
@@ -139,7 +139,7 @@ public abstract class MethodMatchers {
 		}
 
 		@Override
-		public boolean matches(Method method, Class<?> targetClass, Object... args) {
+		public boolean matches(Method method, @Nullable Class<?> targetClass, Object... args) {
 			return this.mm1.matches(method, targetClass, args) || this.mm2.matches(method, targetClass, args);
 		}
 
@@ -230,13 +230,13 @@ public abstract class MethodMatchers {
 		}
 
 		@Override
-		public boolean matches(Method method, Class<?> targetClass, boolean hasIntroductions) {
+		public boolean matches(Method method, @Nullable Class<?> targetClass, boolean hasIntroductions) {
 			return MethodMatchers.matches(this.mm1, method, targetClass, hasIntroductions) &&
 					MethodMatchers.matches(this.mm2, method, targetClass, hasIntroductions);
 		}
 
 		@Override
-		public boolean matches(Method method, Class<?> targetClass) {
+		public boolean matches(Method method, @Nullable Class<?> targetClass) {
 			return this.mm1.matches(method, targetClass) && this.mm2.matches(method, targetClass);
 		}
 
@@ -246,7 +246,7 @@ public abstract class MethodMatchers {
 		}
 
 		@Override
-		public boolean matches(Method method, Class<?> targetClass, Object... args) {
+		public boolean matches(Method method, @Nullable Class<?> targetClass, Object... args) {
 			// Because a dynamic intersection may be composed of a static and dynamic part,
 			// we must avoid calling the 3-arg matches method on a dynamic matcher, as
 			// it will probably be an unsupported operation.

spring-aop/src/main/java/org/springframework/aop/support/NameMatchMethodPointcut.java

@@ -22,6 +22,7 @@ import java.util.Arrays;
 import java.util.LinkedList;
 import java.util.List;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.PatternMatchUtils;
 
@@ -78,7 +79,7 @@ public class NameMatchMethodPointcut extends StaticMethodMatcherPointcut impleme
 
 
 	@Override
-	public boolean matches(Method method, Class<?> targetClass) {
+	public boolean matches(Method method, @Nullable Class<?> targetClass) {
 		for (String mappedName : this.mappedNames) {
 			if (mappedName.equals(method.getName()) || isMatch(method.getName(), mappedName)) {
 				return true;

spring-aop/src/main/java/org/springframework/aop/support/Pointcuts.java

@@ -21,6 +21,7 @@ import java.lang.reflect.Method;
 
 import org.springframework.aop.MethodMatcher;
 import org.springframework.aop.Pointcut;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -97,7 +98,7 @@ public abstract class Pointcuts {
 		public static SetterPointcut INSTANCE = new SetterPointcut();
 
 		@Override
-		public boolean matches(Method method, Class<?> targetClass) {
+		public boolean matches(Method method, @Nullable Class<?> targetClass) {
 			return (method.getName().startsWith("set") &&
 					method.getParameterCount() == 1 &&
 					method.getReturnType() == Void.TYPE);
@@ -118,7 +119,7 @@ public abstract class Pointcuts {
 		public static GetterPointcut INSTANCE = new GetterPointcut();
 
 		@Override
-		public boolean matches(Method method, Class<?> targetClass) {
+		public boolean matches(Method method, @Nullable Class<?> targetClass) {
 			return (method.getName().startsWith("get") &&
 					method.getParameterCount() == 0);
 		}

spring-aop/src/main/java/org/springframework/aop/support/StaticMethodMatcher.java

@@ -19,6 +19,7 @@ package org.springframework.aop.support;
 import java.lang.reflect.Method;
 
 import org.springframework.aop.MethodMatcher;
+import org.springframework.lang.Nullable;
 
 /**
  * Convenient abstract superclass for static method matchers, which don't care
@@ -32,7 +33,7 @@ public abstract class StaticMethodMatcher implements MethodMatcher {
 	}
 
 	@Override
-	public final boolean matches(Method method, Class<?> targetClass, Object... args) {
+	public final boolean matches(Method method, @Nullable Class<?> targetClass, Object... args) {
 		// should never be invoked because isRuntime() returns false
 		throw new UnsupportedOperationException("Illegal MethodMatcher usage");
 	}

spring-aop/src/main/java/org/springframework/aop/support/annotation/AnnotationMethodMatcher.java

@@ -22,6 +22,7 @@ import java.lang.reflect.Method;
 import org.springframework.aop.support.AopUtils;
 import org.springframework.aop.support.StaticMethodMatcher;
 import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -66,7 +67,7 @@ public class AnnotationMethodMatcher extends StaticMethodMatcher {
 
 
 	@Override
-	public boolean matches(Method method, Class<?> targetClass) {
+	public boolean matches(Method method, @Nullable Class<?> targetClass) {
 		if (matchesMethod(method)) {
 			return true;
 		}

spring-aop/src/test/java/org/springframework/aop/aspectj/MethodInvocationProceedingJoinPointTests.java

@@ -33,6 +33,7 @@ import org.springframework.aop.framework.AopContext;
 import org.springframework.aop.framework.ProxyFactory;
 import org.springframework.aop.interceptor.ExposeInvocationInterceptor;
 import org.springframework.aop.support.AopUtils;
+import org.springframework.lang.Nullable;
 import org.springframework.tests.sample.beans.ITestBean;
 import org.springframework.tests.sample.beans.TestBean;
 
@@ -81,7 +82,7 @@ public class MethodInvocationProceedingJoinPointTests {
 			private int depth;
 
 			@Override
-			public void before(Method method, Object[] args, Object target) throws Throwable {
+			public void before(Method method, Object[] args, @Nullable Object target) throws Throwable {
 				JoinPoint jp = AbstractAspectJAdvice.currentJoinPoint();
 				assertTrue("Method named in toString", jp.toString().contains(method.getName()));
 				// Ensure that these don't cause problems
@@ -138,7 +139,7 @@ public class MethodInvocationProceedingJoinPointTests {
 		pf.addAdvisor(ExposeInvocationInterceptor.ADVISOR);
 		pf.addAdvice(new MethodBeforeAdvice() {
 			@Override
-			public void before(Method method, Object[] args, Object target) throws Throwable {
+			public void before(Method method, Object[] args, @Nullable Object target) throws Throwable {
 				SourceLocation sloc = AbstractAspectJAdvice.currentJoinPoint().getSourceLocation();
 				assertEquals("Same source location must be returned on subsequent requests", sloc, AbstractAspectJAdvice.currentJoinPoint().getSourceLocation());
 				assertEquals(TestBean.class, sloc.getWithinType());
@@ -171,7 +172,7 @@ public class MethodInvocationProceedingJoinPointTests {
 		pf.addAdvisor(ExposeInvocationInterceptor.ADVISOR);
 		pf.addAdvice(new MethodBeforeAdvice() {
 			@Override
-			public void before(Method method, Object[] args, Object target) throws Throwable {
+			public void before(Method method, Object[] args, @Nullable Object target) throws Throwable {
 				StaticPart staticPart = AbstractAspectJAdvice.currentJoinPoint().getStaticPart();
 				assertEquals("Same static part must be returned on subsequent requests", staticPart, AbstractAspectJAdvice.currentJoinPoint().getStaticPart());
 				assertEquals(ProceedingJoinPoint.METHOD_EXECUTION, staticPart.getKind());
@@ -191,7 +192,7 @@ public class MethodInvocationProceedingJoinPointTests {
 		pf.addAdvisor(ExposeInvocationInterceptor.ADVISOR);
 		pf.addAdvice(new MethodBeforeAdvice() {
 			@Override
-			public void before(Method method, Object[] args, Object target) throws Throwable {
+			public void before(Method method, Object[] args, @Nullable Object target) throws Throwable {
 				// makeEncSJP, although meant for computing the enclosing join point,
 				// it serves our purpose here
 				JoinPoint.StaticPart aspectJVersionJp = Factory.makeEncSJP(method);

spring-aop/src/test/java/org/springframework/aop/aspectj/TrickyAspectJPointcutExpressionTests.java

@@ -32,6 +32,7 @@ import org.springframework.aop.ThrowsAdvice;
 import org.springframework.aop.framework.ProxyFactory;
 import org.springframework.aop.support.DefaultPointcutAdvisor;
 import org.springframework.core.OverridingClassLoader;
+import org.springframework.lang.Nullable;
 
 import static org.junit.Assert.*;
 
@@ -174,7 +175,7 @@ public class TrickyAspectJPointcutExpressionTests {
 		private int countThrows = 0;
 
 		@Override
-		public void before(Method method, Object[] objects, Object o) throws Throwable {
+		public void before(Method method, Object[] objects, @Nullable Object o) throws Throwable {
 			countBefore++;
 		}
 

spring-aop/src/test/java/org/springframework/aop/aspectj/autoproxy/AspectJPrecedenceComparatorTests.java

@@ -33,6 +33,7 @@ import org.springframework.aop.aspectj.AspectJExpressionPointcut;
 import org.springframework.aop.aspectj.AspectJMethodBeforeAdvice;
 import org.springframework.aop.aspectj.AspectJPointcutAdvisor;
 import org.springframework.aop.support.DefaultPointcutAdvisor;
+import org.springframework.lang.Nullable;
 
 import static org.junit.Assert.*;
 
@@ -196,7 +197,7 @@ public class AspectJPrecedenceComparatorTests {
 	private Advisor createSpringAOPAfterAdvice(int order) {
 		AfterReturningAdvice advice = new AfterReturningAdvice() {
 			@Override
-			public void afterReturning(Object returnValue, Method method, Object[] args, Object target) throws Throwable {
+			public void afterReturning(@Nullable Object returnValue, Method method, Object[] args, @Nullable Object target) throws Throwable {
 			}
 		};
 		DefaultPointcutAdvisor advisor = new DefaultPointcutAdvisor(this.anyOldPointcut, advice);

spring-aop/src/test/java/org/springframework/aop/support/AopUtilsTests.java

@@ -25,6 +25,7 @@ import org.springframework.aop.MethodMatcher;
 import org.springframework.aop.Pointcut;
 import org.springframework.aop.interceptor.ExposeInvocationInterceptor;
 import org.springframework.aop.target.EmptyTargetSource;
+import org.springframework.lang.Nullable;
 import org.springframework.tests.aop.interceptor.NopInterceptor;
 import org.springframework.tests.sample.beans.TestBean;
 import org.springframework.util.SerializationTestUtils;
@@ -41,7 +42,7 @@ public class AopUtilsTests {
 	public void testPointcutCanNeverApply() {
 		class TestPointcut extends StaticMethodMatcherPointcut {
 			@Override
-			public boolean matches(Method method, Class<?> clazzy) {
+			public boolean matches(Method method, @Nullable Class<?> clazzy) {
 				return false;
 			}
 		}
@@ -60,7 +61,7 @@ public class AopUtilsTests {
 	public void testPointcutAppliesToOneMethodOnObject() {
 		class TestPointcut extends StaticMethodMatcherPointcut {
 			@Override
-			public boolean matches(Method method, Class<?> clazz) {
+			public boolean matches(Method method, @Nullable Class<?> clazz) {
 				return method.getName().equals("hashCode");
 			}
 		}

spring-aop/src/test/java/org/springframework/aop/support/ComposablePointcutTests.java

@@ -24,6 +24,7 @@ import org.springframework.aop.ClassFilter;
 import org.springframework.aop.MethodMatcher;
 import org.springframework.aop.Pointcut;
 import org.springframework.core.NestedRuntimeException;
+import org.springframework.lang.Nullable;
 import org.springframework.tests.sample.beans.TestBean;
 
 import static org.junit.Assert.*;
@@ -36,28 +37,28 @@ public class ComposablePointcutTests {
 
 	public static MethodMatcher GETTER_METHOD_MATCHER = new StaticMethodMatcher() {
 		@Override
-		public boolean matches(Method m, Class<?> targetClass) {
+		public boolean matches(Method m, @Nullable Class<?> targetClass) {
 			return m.getName().startsWith("get");
 		}
 	};
 
 	public static MethodMatcher GET_AGE_METHOD_MATCHER = new StaticMethodMatcher() {
 		@Override
-		public boolean matches(Method m, Class<?> targetClass) {
+		public boolean matches(Method m, @Nullable Class<?> targetClass) {
 			return m.getName().equals("getAge");
 		}
 	};
 
 	public static MethodMatcher ABSQUATULATE_METHOD_MATCHER = new StaticMethodMatcher() {
 		@Override
-		public boolean matches(Method m, Class<?> targetClass) {
+		public boolean matches(Method m, @Nullable Class<?> targetClass) {
 			return m.getName().equals("absquatulate");
 		}
 	};
 
 	public static MethodMatcher SETTER_METHOD_MATCHER = new StaticMethodMatcher() {
 		@Override
-		public boolean matches(Method m, Class<?> targetClass) {
+		public boolean matches(Method m, @Nullable Class<?> targetClass) {
 			return m.getName().startsWith("set");
 		}
 	};

spring-aop/src/test/java/org/springframework/aop/support/MethodMatchersTests.java

@@ -21,6 +21,7 @@ import java.lang.reflect.Method;
 import org.junit.Test;
 
 import org.springframework.aop.MethodMatcher;
+import org.springframework.lang.Nullable;
 import org.springframework.tests.sample.beans.IOther;
 import org.springframework.tests.sample.beans.ITestBean;
 import org.springframework.tests.sample.beans.TestBean;
@@ -120,7 +121,7 @@ public class MethodMatchersTests {
 		}
 
 		@Override
-		public boolean matches(Method m, Class<?> targetClass) {
+		public boolean matches(Method m, @Nullable Class<?> targetClass) {
 			return m.getName().startsWith(prefix);
 		}
 	}
@@ -129,7 +130,7 @@ public class MethodMatchersTests {
 	private static class TestDynamicMethodMatcherWhichMatches extends DynamicMethodMatcher {
 
 		@Override
-		public boolean matches(Method m, Class<?> targetClass, Object... args) {
+		public boolean matches(Method m, @Nullable Class<?> targetClass, Object... args) {
 			return true;
 		}
 	}
@@ -138,7 +139,7 @@ public class MethodMatchersTests {
 	private static class TestDynamicMethodMatcherWhichDoesNotMatch extends DynamicMethodMatcher {
 
 		@Override
-		public boolean matches(Method m, Class<?> targetClass, Object... args) {
+		public boolean matches(Method m, @Nullable Class<?> targetClass, Object... args) {
 			return false;
 		}
 	}

spring-aop/src/test/java/org/springframework/aop/support/PointcutsTests.java

@@ -22,6 +22,7 @@ import org.junit.Test;
 
 import org.springframework.aop.ClassFilter;
 import org.springframework.aop.Pointcut;
+import org.springframework.lang.Nullable;
 import org.springframework.tests.sample.beans.TestBean;
 
 import static org.junit.Assert.*;
@@ -64,7 +65,7 @@ public class PointcutsTests {
 		}
 
 		@Override
-		public boolean matches(Method m, Class<?> targetClass) {
+		public boolean matches(Method m, @Nullable Class<?> targetClass) {
 			return true;
 		}
 	};
@@ -82,7 +83,7 @@ public class PointcutsTests {
 		}
 
 		@Override
-		public boolean matches(Method m, Class<?> targetClass) {
+		public boolean matches(Method m, @Nullable Class<?> targetClass) {
 			return m.getName().startsWith("set");
 		}
 	};
@@ -95,7 +96,7 @@ public class PointcutsTests {
 		}
 
 		@Override
-		public boolean matches(Method m, Class<?> targetClass) {
+		public boolean matches(Method m, @Nullable Class<?> targetClass) {
 			return m.getName().startsWith("get");
 		}
 	};
@@ -111,7 +112,7 @@ public class PointcutsTests {
 		}
 
 		@Override
-		public boolean matches(Method m, Class<?> targetClass) {
+		public boolean matches(Method m, @Nullable Class<?> targetClass) {
 			return m.getName().startsWith("get");
 		}
 	};

spring-beans/src/main/java/org/springframework/beans/BeanMetadataAttributeAccessor.java

@@ -67,7 +67,7 @@ public class BeanMetadataAttributeAccessor extends AttributeAccessorSupport impl
 	}
 
 	@Override
-	public void setAttribute(String name, Object value) {
+	public void setAttribute(String name, @Nullable Object value) {
 		super.setAttribute(name, new BeanMetadataAttribute(name, value));
 	}
 

spring-beans/src/main/java/org/springframework/beans/PropertyEditorRegistrySupport.java

@@ -284,7 +284,7 @@ public class PropertyEditorRegistrySupport implements PropertyEditorRegistry {
 	}
 
 	@Override
-	public void registerCustomEditor(Class<?> requiredType, String propertyPath, PropertyEditor propertyEditor) {
+	public void registerCustomEditor(@Nullable Class<?> requiredType, @Nullable String propertyPath, PropertyEditor propertyEditor) {
 		if (requiredType == null && propertyPath == null) {
 			throw new IllegalArgumentException("Either requiredType or propertyPath is required");
 		}
@@ -304,7 +304,8 @@ public class PropertyEditorRegistrySupport implements PropertyEditorRegistry {
 	}
 
 	@Override
-	public PropertyEditor findCustomEditor(Class<?> requiredType, String propertyPath) {
+	@Nullable
+	public PropertyEditor findCustomEditor(@Nullable Class<?> requiredType, @Nullable String propertyPath) {
 		Class<?> requiredTypeToUse = requiredType;
 		if (propertyPath != null) {
 			if (this.customEditorsForPath != null) {

spring-beans/src/main/java/org/springframework/beans/TypeConverterSupport.java

@@ -21,6 +21,7 @@ import java.lang.reflect.Field;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.convert.ConversionException;
 import org.springframework.core.convert.ConverterNotFoundException;
+import org.springframework.lang.Nullable;
 
 /**
  * Base implementation of the {@link TypeConverter} interface, using a package-private delegate.
@@ -36,25 +37,25 @@ public abstract class TypeConverterSupport extends PropertyEditorRegistrySupport
 
 
 	@Override
-	public <T> T convertIfNecessary(Object value, Class<T> requiredType) throws TypeMismatchException {
+	public <T> T convertIfNecessary(Object value, @Nullable Class<T> requiredType) throws TypeMismatchException {
 		return doConvert(value, requiredType, null, null);
 	}
 
 	@Override
-	public <T> T convertIfNecessary(Object value, Class<T> requiredType, MethodParameter methodParam)
+	public <T> T convertIfNecessary(Object value, @Nullable Class<T> requiredType, @Nullable MethodParameter methodParam)
 			throws TypeMismatchException {
 
 		return doConvert(value, requiredType, methodParam, null);
 	}
 
 	@Override
-	public <T> T convertIfNecessary(Object value, Class<T> requiredType, Field field)
+	public <T> T convertIfNecessary(Object value, @Nullable Class<T> requiredType, @Nullable Field field)
 			throws TypeMismatchException {
 
 		return doConvert(value, requiredType, null, field);
 	}
 
-	private <T> T doConvert(Object value, Class<T> requiredType, MethodParameter methodParam, Field field)
+	private <T> T doConvert(Object value, Class<T> requiredType, @Nullable MethodParameter methodParam, @Nullable Field field)
 			throws TypeMismatchException {
 		try {
 			if (field != null) {

spring-beans/src/main/java/org/springframework/beans/factory/annotation/CustomAutowireConfigurer.java

@@ -25,6 +25,7 @@ import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.core.Ordered;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 
 /**
@@ -65,7 +66,7 @@ public class CustomAutowireConfigurer implements BeanFactoryPostProcessor, BeanC
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader beanClassLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader beanClassLoader) {
 		this.beanClassLoader = beanClassLoader;
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/config/AbstractFactoryBean.java

@@ -91,7 +91,7 @@ public abstract class AbstractFactoryBean<T>
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		this.beanClassLoader = classLoader;
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/config/CustomScopeConfigurer.java

@@ -23,6 +23,7 @@ import org.springframework.beans.BeanUtils;
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.core.Ordered;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 
@@ -86,7 +87,7 @@ public class CustomScopeConfigurer implements BeanFactoryPostProcessor, BeanClas
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader beanClassLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader beanClassLoader) {
 		this.beanClassLoader = beanClassLoader;
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/config/EmbeddedValueResolver.java

@@ -16,6 +16,7 @@
 
 package org.springframework.beans.factory.config;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.StringValueResolver;
 
 /**
@@ -47,7 +48,7 @@ public class EmbeddedValueResolver implements StringValueResolver {
 
 
 	@Override
-	public String resolveStringValue(String strVal) {
+	public String resolveStringValue(@Nullable String strVal) {
 		String value = this.exprContext.getBeanFactory().resolveEmbeddedValue(strVal);
 		if (this.exprResolver != null && value != null) {
 			Object evaluated = this.exprResolver.evaluate(value, this.exprContext);

spring-beans/src/main/java/org/springframework/beans/factory/config/FieldRetrievingFactoryBean.java

@@ -24,6 +24,7 @@ import org.springframework.beans.factory.BeanNameAware;
 import org.springframework.beans.factory.FactoryBean;
 import org.springframework.beans.factory.FactoryBeanNotInitializedException;
 import org.springframework.beans.factory.InitializingBean;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ReflectionUtils;
 import org.springframework.util.StringUtils;
@@ -148,7 +149,7 @@ public class FieldRetrievingFactoryBean
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		this.beanClassLoader = classLoader;
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/config/MethodInvokingBean.java

@@ -24,6 +24,7 @@ import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.support.ArgumentConvertingMethodInvoker;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 
 /**
@@ -72,7 +73,7 @@ public class MethodInvokingBean extends ArgumentConvertingMethodInvoker
 
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		this.beanClassLoader = classLoader;
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/config/PropertyPlaceholderConfigurer.java

@@ -238,7 +238,8 @@ public class PropertyPlaceholderConfigurer extends PlaceholderConfigurerSupport
 		}
 
 		@Override
-		public String resolveStringValue(String strVal) throws BeansException {
+		@Nullable
+		public String resolveStringValue(@Nullable String strVal) throws BeansException {
 			String resolved = this.helper.replacePlaceholders(strVal, this.resolver);
 			if (trimValues) {
 				resolved = resolved.trim();

spring-beans/src/main/java/org/springframework/beans/factory/parsing/NullSourceExtractor.java

@@ -17,6 +17,7 @@
 package org.springframework.beans.factory.parsing;
 
 import org.springframework.core.io.Resource;
+import org.springframework.lang.Nullable;
 
 /**
  * Simple implementation of {@link SourceExtractor} that returns {@code null}
@@ -34,7 +35,8 @@ public class NullSourceExtractor implements SourceExtractor {
 	 * This implementation simply returns {@code null} for any input.
 	 */
 	@Override
-	public Object extractSource(Object sourceCandidate, Resource definitionResource) {
+	@Nullable
+	public Object extractSource(Object sourceCandidate, @Nullable Resource definitionResource) {
 		return null;
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/parsing/PassThroughSourceExtractor.java

@@ -17,6 +17,7 @@
 package org.springframework.beans.factory.parsing;
 
 import org.springframework.core.io.Resource;
+import org.springframework.lang.Nullable;
 
 /**
  * Simple {@link SourceExtractor} implementation that just passes
@@ -40,7 +41,7 @@ public class PassThroughSourceExtractor implements SourceExtractor {
 	 * @return the supplied {@code sourceCandidate}
 	 */
 	@Override
-	public Object extractSource(Object sourceCandidate, Resource definingResource) {
+	public Object extractSource(Object sourceCandidate, @Nullable Resource definingResource) {
 		return sourceCandidate;
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/serviceloader/AbstractServiceLoaderBasedFactoryBean.java

@@ -20,6 +20,7 @@ import java.util.ServiceLoader;
 
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.beans.factory.config.AbstractFactoryBean;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 
@@ -54,7 +55,7 @@ public abstract class AbstractServiceLoaderBasedFactoryBean extends AbstractFact
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader beanClassLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader beanClassLoader) {
 		this.beanClassLoader = beanClassLoader;
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/support/AbstractBeanFactory.java

@@ -195,7 +195,7 @@ public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport imp
 	}
 
 	@Override
-	public <T> T getBean(String name, Class<T> requiredType) throws BeansException {
+	public <T> T getBean(String name, @Nullable Class<T> requiredType) throws BeansException {
 		return doGetBean(name, requiredType, null, false);
 	}
 
@@ -698,7 +698,7 @@ public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport imp
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader beanClassLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader beanClassLoader) {
 		this.beanClassLoader = (beanClassLoader != null ? beanClassLoader : ClassUtils.getDefaultClassLoader());
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/support/ChildBeanDefinition.java

@@ -18,6 +18,7 @@ package org.springframework.beans.factory.support;
 
 import org.springframework.beans.MutablePropertyValues;
 import org.springframework.beans.factory.config.ConstructorArgumentValues;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -129,7 +130,7 @@ public class ChildBeanDefinition extends AbstractBeanDefinition {
 
 
 	@Override
-	public void setParentName(String parentName) {
+	public void setParentName(@Nullable String parentName) {
 		this.parentName = parentName;
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultListableBeanFactory.java

@@ -373,17 +373,17 @@ public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFacto
 	}
 
 	@Override
-	public String[] getBeanNamesForType(ResolvableType type) {
+	public String[] getBeanNamesForType(@Nullable ResolvableType type) {
 		return doGetBeanNamesForType(type, true, true);
 	}
 
 	@Override
-	public String[] getBeanNamesForType(Class<?> type) {
+	public String[] getBeanNamesForType(@Nullable Class<?> type) {
 		return getBeanNamesForType(type, true, true);
 	}
 
 	@Override
-	public String[] getBeanNamesForType(Class<?> type, boolean includeNonSingletons, boolean allowEagerInit) {
+	public String[] getBeanNamesForType(@Nullable Class<?> type, boolean includeNonSingletons, boolean allowEagerInit) {
 		if (!isConfigurationFrozen() || type == null || !allowEagerInit) {
 			return doGetBeanNamesForType(ResolvableType.forRawClass(type), includeNonSingletons, allowEagerInit);
 		}
@@ -497,12 +497,12 @@ public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFacto
 	}
 
 	@Override
-	public <T> Map<String, T> getBeansOfType(Class<T> type) throws BeansException {
+	public <T> Map<String, T> getBeansOfType(@Nullable Class<T> type) throws BeansException {
 		return getBeansOfType(type, true, true);
 	}
 
 	@Override
-	public <T> Map<String, T> getBeansOfType(Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
+	public <T> Map<String, T> getBeansOfType(@Nullable Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
 			throws BeansException {
 
 		String[] beanNames = getBeanNamesForType(type, includeNonSingletons, allowEagerInit);

spring-beans/src/main/java/org/springframework/beans/factory/support/GenericBeanDefinition.java

@@ -17,6 +17,7 @@
 package org.springframework.beans.factory.support;
 
 import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.lang.Nullable;
 
 /**
  * GenericBeanDefinition is a one-stop shop for standard bean definition purposes.
@@ -64,7 +65,7 @@ public class GenericBeanDefinition extends AbstractBeanDefinition {
 
 
 	@Override
-	public void setParentName(String parentName) {
+	public void setParentName(@Nullable String parentName) {
 		this.parentName = parentName;
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/support/ManagedList.java

@@ -21,6 +21,7 @@ import java.util.List;
 
 import org.springframework.beans.BeanMetadataElement;
 import org.springframework.beans.Mergeable;
+import org.springframework.lang.Nullable;
 
 /**
  * Tag collection class used to hold managed List elements, which may
@@ -91,7 +92,7 @@ public class ManagedList<E> extends ArrayList<E> implements Mergeable, BeanMetad
 
 	@Override
 	@SuppressWarnings("unchecked")
-	public List<E> merge(Object parent) {
+	public List<E> merge(@Nullable Object parent) {
 		if (!this.mergeEnabled) {
 			throw new IllegalStateException("Not allowed to merge when the 'mergeEnabled' property is set to 'false'");
 		}

spring-beans/src/main/java/org/springframework/beans/factory/support/ManagedMap.java

@@ -21,6 +21,7 @@ import java.util.Map;
 
 import org.springframework.beans.BeanMetadataElement;
 import org.springframework.beans.Mergeable;
+import org.springframework.lang.Nullable;
 
 /**
  * Tag collection class used to hold managed Map values, which may
@@ -106,7 +107,7 @@ public class ManagedMap<K, V> extends LinkedHashMap<K, V> implements Mergeable,
 
 	@Override
 	@SuppressWarnings("unchecked")
-	public Object merge(Object parent) {
+	public Object merge(@Nullable Object parent) {
 		if (!this.mergeEnabled) {
 			throw new IllegalStateException("Not allowed to merge when the 'mergeEnabled' property is set to 'false'");
 		}

spring-beans/src/main/java/org/springframework/beans/factory/support/ManagedProperties.java

@@ -20,6 +20,7 @@ import java.util.Properties;
 
 import org.springframework.beans.BeanMetadataElement;
 import org.springframework.beans.Mergeable;
+import org.springframework.lang.Nullable;
 
 /**
  * Tag class which represents a Spring-managed {@link Properties} instance
@@ -65,7 +66,7 @@ public class ManagedProperties extends Properties implements Mergeable, BeanMeta
 
 
 	@Override
-	public Object merge(Object parent) {
+	public Object merge(@Nullable Object parent) {
 		if (!this.mergeEnabled) {
 			throw new IllegalStateException("Not allowed to merge when the 'mergeEnabled' property is set to 'false'");
 		}

spring-beans/src/main/java/org/springframework/beans/factory/support/ManagedSet.java

@@ -21,6 +21,7 @@ import java.util.Set;
 
 import org.springframework.beans.BeanMetadataElement;
 import org.springframework.beans.Mergeable;
+import org.springframework.lang.Nullable;
 
 /**
  * Tag collection class used to hold managed Set values, which may
@@ -90,7 +91,7 @@ public class ManagedSet<E> extends LinkedHashSet<E> implements Mergeable, BeanMe
 
 	@Override
 	@SuppressWarnings("unchecked")
-	public Set<E> merge(Object parent) {
+	public Set<E> merge(@Nullable Object parent) {
 		if (!this.mergeEnabled) {
 			throw new IllegalStateException("Not allowed to merge when the 'mergeEnabled' property is set to 'false'");
 		}

spring-beans/src/main/java/org/springframework/beans/factory/support/RootBeanDefinition.java

@@ -236,7 +236,7 @@ public class RootBeanDefinition extends AbstractBeanDefinition {
 	}
 
 	@Override
-	public void setParentName(String parentName) {
+	public void setParentName(@Nullable String parentName) {
 		if (parentName != null) {
 			throw new IllegalArgumentException("Root bean cannot be changed into a child bean with parent reference");
 		}

spring-beans/src/main/java/org/springframework/beans/factory/support/SimpleInstantiationStrategy.java

@@ -58,7 +58,7 @@ public class SimpleInstantiationStrategy implements InstantiationStrategy {
 
 
 	@Override
-	public Object instantiate(RootBeanDefinition bd, String beanName, BeanFactory owner) {
+	public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) {
 		// Don't override the class with CGLIB if no overrides.
 		if (bd.getMethodOverrides().isEmpty()) {
 			Constructor<?> constructorToUse;
@@ -107,7 +107,7 @@ public class SimpleInstantiationStrategy implements InstantiationStrategy {
 	}
 
 	@Override
-	public Object instantiate(RootBeanDefinition bd, String beanName, BeanFactory owner,
+	public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner,
 			final Constructor<?> ctor, Object... args) {
 
 		if (bd.getMethodOverrides().isEmpty()) {
@@ -141,8 +141,8 @@ public class SimpleInstantiationStrategy implements InstantiationStrategy {
 	}
 
 	@Override
-	public Object instantiate(RootBeanDefinition bd, String beanName, BeanFactory owner,
+	public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner,
-			Object factoryBean, final Method factoryMethod, Object... args) {
+			@Nullable Object factoryBean, final Method factoryMethod, Object... args) {
 
 		try {
 			if (System.getSecurityManager() != null) {

spring-beans/src/main/java/org/springframework/beans/factory/support/StaticListableBeanFactory.java

@@ -34,6 +34,7 @@ import org.springframework.beans.factory.NoUniqueBeanDefinitionException;
 import org.springframework.beans.factory.SmartFactoryBean;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -132,7 +133,7 @@ public class StaticListableBeanFactory implements ListableBeanFactory {
 
 	@Override
 	@SuppressWarnings("unchecked")
-	public <T> T getBean(String name, Class<T> requiredType) throws BeansException {
+	public <T> T getBean(String name, @Nullable Class<T> requiredType) throws BeansException {
 		Object bean = getBean(name);
 		if (requiredType != null && !requiredType.isAssignableFrom(bean.getClass())) {
 			throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
@@ -247,7 +248,7 @@ public class StaticListableBeanFactory implements ListableBeanFactory {
 	}
 
 	@Override
-	public String[] getBeanNamesForType(ResolvableType type) {
+	public String[] getBeanNamesForType(@Nullable ResolvableType type) {
 		boolean isFactoryType = false;
 		if (type != null) {
 			Class<?> resolved = type.resolve();
@@ -275,23 +276,23 @@ public class StaticListableBeanFactory implements ListableBeanFactory {
 	}
 
 	@Override
-	public String[] getBeanNamesForType(Class<?> type) {
+	public String[] getBeanNamesForType(@Nullable Class<?> type) {
 		return getBeanNamesForType(ResolvableType.forClass(type));
 	}
 
 	@Override
-	public String[] getBeanNamesForType(Class<?> type, boolean includeNonSingletons, boolean allowEagerInit) {
+	public String[] getBeanNamesForType(@Nullable Class<?> type, boolean includeNonSingletons, boolean allowEagerInit) {
 		return getBeanNamesForType(ResolvableType.forClass(type));
 	}
 
 	@Override
-	public <T> Map<String, T> getBeansOfType(Class<T> type) throws BeansException {
+	public <T> Map<String, T> getBeansOfType(@Nullable Class<T> type) throws BeansException {
 		return getBeansOfType(type, true, true);
 	}
 
 	@Override
 	@SuppressWarnings("unchecked")
-	public <T> Map<String, T> getBeansOfType(Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
+	public <T> Map<String, T> getBeansOfType(@Nullable Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
 			throws BeansException {
 
 		boolean isFactoryType = (type != null && FactoryBean.class.isAssignableFrom(type));

spring-beans/src/main/java/org/springframework/beans/factory/xml/AbstractBeanDefinitionParser.java

@@ -25,6 +25,7 @@ import org.springframework.beans.factory.parsing.BeanComponentDefinition;
 import org.springframework.beans.factory.support.AbstractBeanDefinition;
 import org.springframework.beans.factory.support.BeanDefinitionReaderUtils;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 
 /**
@@ -147,7 +148,7 @@ public abstract class AbstractBeanDefinitionParser implements BeanDefinitionPars
 	 * @see #parse(org.w3c.dom.Element, ParserContext)
 	 * @see #postProcessComponentDefinition(org.springframework.beans.factory.parsing.BeanComponentDefinition)
 	 */
-	protected abstract AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext);
+	protected abstract AbstractBeanDefinition parseInternal(@Nullable Element element, @Nullable ParserContext parserContext);
 
 	/**
 	 * Should an ID be generated instead of read from the passed in {@link Element}?

spring-beans/src/main/java/org/springframework/beans/factory/xml/AbstractSingleBeanDefinitionParser.java

@@ -58,7 +58,7 @@ public abstract class AbstractSingleBeanDefinitionParser extends AbstractBeanDef
 	 * @see #doParse
 	 */
 	@Override
-	protected final AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext) {
+	protected final AbstractBeanDefinition parseInternal(@Nullable Element element, @Nullable ParserContext parserContext) {
 		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition();
 		String parentName = getParentName(element);
 		if (parentName != null) {

spring-beans/src/test/java/org/springframework/beans/AbstractPropertyAccessorTests.java

@@ -49,6 +49,7 @@ import org.springframework.core.convert.ConversionFailedException;
 import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.core.convert.support.GenericConversionService;
+import org.springframework.lang.Nullable;
 import org.springframework.tests.Assume;
 import org.springframework.tests.TestGroup;
 import org.springframework.tests.sample.beans.BooleanTestBean;
@@ -461,7 +462,7 @@ public abstract class AbstractPropertyAccessorTests {
 		AbstractPropertyAccessor accessor = createAccessor(target);
 		accessor.setConversionService(new GenericConversionService() {
 			@Override
-			public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+			public Object convert(@Nullable Object source, @Nullable TypeDescriptor sourceType, TypeDescriptor targetType) {
 				throw new ConversionFailedException(sourceType, targetType, source, null);
 			}
 		});

spring-beans/src/test/java/org/springframework/beans/factory/DefaultListableBeanFactoryTests.java

@@ -83,6 +83,7 @@ import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.core.convert.support.GenericConversionService;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.UrlResource;
+import org.springframework.lang.Nullable;
 import org.springframework.tests.Assume;
 import org.springframework.tests.TestGroup;
 import org.springframework.tests.sample.beans.DependenciesBean;
@@ -3120,7 +3121,7 @@ public class DefaultListableBeanFactoryTests {
 
 		@Override
 		@SuppressWarnings("unchecked")
-		public Object convertIfNecessary(Object value, Class requiredType) {
+		public Object convertIfNecessary(Object value, @Nullable Class requiredType) {
 			if (value instanceof String && Float.class.isAssignableFrom(requiredType)) {
 				try {
 					return new Float(this.numberFormat.parse((String) value).floatValue());
@@ -3139,13 +3140,13 @@ public class DefaultListableBeanFactoryTests {
 
 		@Override
 		@SuppressWarnings("unchecked")
-		public Object convertIfNecessary(Object value, Class requiredType, MethodParameter methodParam) {
+		public Object convertIfNecessary(Object value, @Nullable Class requiredType, @Nullable MethodParameter methodParam) {
 			return convertIfNecessary(value, requiredType);
 		}
 
 		@Override
 		@SuppressWarnings("unchecked")
-		public Object convertIfNecessary(Object value, Class requiredType, Field field) {
+		public Object convertIfNecessary(Object value, @Nullable Class requiredType, @Nullable Field field) {
 			return convertIfNecessary(value, requiredType);
 		}
 	}

spring-context-support/src/main/java/org/springframework/cache/caffeine/CaffeineCache.java

@@ -22,6 +22,7 @@ import java.util.function.Function;
 import com.github.benmanes.caffeine.cache.LoadingCache;
 
 import org.springframework.cache.support.AbstractValueAdaptingCache;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -82,7 +83,7 @@ public class CaffeineCache extends AbstractValueAdaptingCache {
 	}
 
 	@Override
-	public ValueWrapper get(Object key) {
+	public ValueWrapper get(@Nullable Object key) {
 		if (this.cache instanceof LoadingCache) {
 			Object value = ((LoadingCache<Object, Object>) this.cache).get(key);
 			return toValueWrapper(value);
@@ -92,7 +93,8 @@ public class CaffeineCache extends AbstractValueAdaptingCache {
 
 	@SuppressWarnings("unchecked")
 	@Override
-	public <T> T get(Object key, final Callable<T> valueLoader) {
+	@Nullable
+	public <T> T get(@Nullable Object key, final Callable<T> valueLoader) {
 		return (T) fromStoreValue(this.cache.get(key, new LoadFunction(valueLoader)));
 	}
 
@@ -102,19 +104,20 @@ public class CaffeineCache extends AbstractValueAdaptingCache {
 	}
 
 	@Override
-	public void put(Object key, Object value) {
+	public void put(@Nullable Object key, @Nullable Object value) {
 		this.cache.put(key, toStoreValue(value));
 	}
 
 	@Override
-	public ValueWrapper putIfAbsent(Object key, final Object value) {
+	@Nullable
+	public ValueWrapper putIfAbsent(@Nullable Object key, @Nullable final Object value) {
 		PutIfAbsentFunction callable = new PutIfAbsentFunction(value);
 		Object result = this.cache.get(key, callable);
 		return (callable.called ? null : toValueWrapper(result));
 	}
 
 	@Override
-	public void evict(Object key) {
+	public void evict(@Nullable Object key) {
 		this.cache.invalidate(key);
 	}
 

spring-context-support/src/main/java/org/springframework/cache/ehcache/EhCacheCache.java

@@ -24,6 +24,7 @@ import net.sf.ehcache.Status;
 
 import org.springframework.cache.Cache;
 import org.springframework.cache.support.SimpleValueWrapper;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -63,14 +64,15 @@ public class EhCacheCache implements Cache {
 	}
 
 	@Override
-	public ValueWrapper get(Object key) {
+	public ValueWrapper get(@Nullable Object key) {
 		Element element = lookup(key);
 		return toValueWrapper(element);
 	}
 
 	@SuppressWarnings("unchecked")
 	@Override
-	public <T> T get(Object key, Callable<T> valueLoader) {
+	@Nullable
+	public <T> T get(@Nullable Object key, Callable<T> valueLoader) {
 		Element element = lookup(key);
 		if (element != null) {
 			return (T) element.getObjectValue();
@@ -107,7 +109,8 @@ public class EhCacheCache implements Cache {
 
 	@Override
 	@SuppressWarnings("unchecked")
-	public <T> T get(Object key, Class<T> type) {
+	@Nullable
+	public <T> T get(@Nullable Object key, Class<T> type) {
 		Element element = this.cache.get(key);
 		Object value = (element != null ? element.getObjectValue() : null);
 		if (value != null && type != null && !type.isInstance(value)) {
@@ -117,18 +120,18 @@ public class EhCacheCache implements Cache {
 	}
 
 	@Override
-	public void put(Object key, Object value) {
+	public void put(@Nullable Object key, @Nullable Object value) {
 		this.cache.put(new Element(key, value));
 	}
 
 	@Override
-	public ValueWrapper putIfAbsent(Object key, Object value) {
+	public ValueWrapper putIfAbsent(@Nullable Object key, @Nullable Object value) {
 		Element existingElement = this.cache.putIfAbsent(new Element(key, value));
 		return toValueWrapper(existingElement);
 	}
 
 	@Override
-	public void evict(Object key) {
+	public void evict(@Nullable Object key) {
 		this.cache.remove(key);
 	}
 

spring-context-support/src/main/java/org/springframework/cache/jcache/JCacheCache.java

@@ -22,6 +22,7 @@ import javax.cache.processor.EntryProcessorException;
 import javax.cache.processor.MutableEntry;
 
 import org.springframework.cache.support.AbstractValueAdaptingCache;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -75,7 +76,7 @@ public class JCacheCache extends AbstractValueAdaptingCache {
 	}
 
 	@Override
-	public <T> T get(Object key, Callable<T> valueLoader) {
+	public <T> T get(@Nullable Object key, Callable<T> valueLoader) {
 		try {
 			return this.cache.invoke(key, new ValueLoaderEntryProcessor<T>(), valueLoader);
 		}
@@ -85,18 +86,18 @@ public class JCacheCache extends AbstractValueAdaptingCache {
 	}
 
 	@Override
-	public void put(Object key, Object value) {
+	public void put(@Nullable Object key, @Nullable Object value) {
 		this.cache.put(key, toStoreValue(value));
 	}
 
 	@Override
-	public ValueWrapper putIfAbsent(Object key, Object value) {
+	public ValueWrapper putIfAbsent(@Nullable Object key, @Nullable Object value) {
 		boolean set = this.cache.putIfAbsent(key, toStoreValue(value));
 		return (set ? null : get(key));
 	}
 
 	@Override
-	public void evict(Object key) {
+	public void evict(@Nullable Object key) {
 		this.cache.remove(key);
 	}
 

spring-context-support/src/main/java/org/springframework/cache/jcache/JCacheManagerFactoryBean.java

@@ -69,7 +69,7 @@ public class JCacheManagerFactoryBean
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		this.beanClassLoader = classLoader;
 	}
 

spring-context-support/src/main/java/org/springframework/cache/jcache/config/AbstractJCacheConfiguration.java

@@ -25,6 +25,7 @@ import org.springframework.cache.jcache.interceptor.JCacheOperationSource;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Role;
+import org.springframework.lang.Nullable;
 
 /**
  * Abstract JSR-107 specific {@code @Configuration} class providing common
@@ -40,7 +41,7 @@ public class AbstractJCacheConfiguration extends AbstractCachingConfiguration {
 	protected CacheResolver exceptionCacheResolver;
 
 	@Override
-	protected void useCachingConfigurer(CachingConfigurer config) {
+	protected void useCachingConfigurer(@Nullable CachingConfigurer config) {
 		super.useCachingConfigurer(config);
 		if (config instanceof JCacheConfigurer) {
 			this.exceptionCacheResolver = ((JCacheConfigurer) config).exceptionCacheResolver();

spring-context-support/src/main/java/org/springframework/cache/transaction/TransactionAwareCacheDecorator.java

@@ -19,6 +19,7 @@ package org.springframework.cache.transaction;
 import java.util.concurrent.Callable;
 
 import org.springframework.cache.Cache;
+import org.springframework.lang.Nullable;
 import org.springframework.transaction.support.TransactionSynchronizationAdapter;
 import org.springframework.transaction.support.TransactionSynchronizationManager;
 import org.springframework.util.Assert;
@@ -71,22 +72,22 @@ public class TransactionAwareCacheDecorator implements Cache {
 	}
 
 	@Override
-	public ValueWrapper get(Object key) {
+	public ValueWrapper get(@Nullable Object key) {
 		return this.targetCache.get(key);
 	}
 
 	@Override
-	public <T> T get(Object key, Class<T> type) {
+	public <T> T get(@Nullable Object key, Class<T> type) {
 		return this.targetCache.get(key, type);
 	}
 
 	@Override
-	public <T> T get(Object key, Callable<T> valueLoader) {
+	public <T> T get(@Nullable Object key, Callable<T> valueLoader) {
 		return this.targetCache.get(key, valueLoader);
 	}
 
 	@Override
-	public void put(final Object key, final Object value) {
+	public void put(@Nullable final Object key, @Nullable final Object value) {
 		if (TransactionSynchronizationManager.isSynchronizationActive()) {
 			TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronizationAdapter() {
 				@Override
@@ -101,12 +102,12 @@ public class TransactionAwareCacheDecorator implements Cache {
 	}
 
 	@Override
-	public ValueWrapper putIfAbsent(final Object key, final Object value) {
+	public ValueWrapper putIfAbsent(@Nullable final Object key, @Nullable final Object value) {
 		return this.targetCache.putIfAbsent(key, value);
 	}
 
 	@Override
-	public void evict(final Object key) {
+	public void evict(@Nullable final Object key) {
 		if (TransactionSynchronizationManager.isSynchronizationActive()) {
 			TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronizationAdapter() {
 				@Override

spring-context-support/src/main/java/org/springframework/scheduling/quartz/MethodInvokingJobDetailFactoryBean.java

@@ -35,6 +35,7 @@ import org.springframework.beans.factory.BeanNameAware;
 import org.springframework.beans.factory.FactoryBean;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.support.ArgumentConvertingMethodInvoker;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.MethodInvoker;
@@ -141,7 +142,7 @@ public class MethodInvokingJobDetailFactoryBean extends ArgumentConvertingMethod
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		this.beanClassLoader = classLoader;
 	}
 

spring-context/src/main/java/org/springframework/cache/annotation/AbstractCachingConfiguration.java

@@ -27,6 +27,7 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.ImportAware;
 import org.springframework.core.annotation.AnnotationAttributes;
 import org.springframework.core.type.AnnotationMetadata;
+import org.springframework.lang.Nullable;
 import org.springframework.util.CollectionUtils;
 
 /**
@@ -80,7 +81,7 @@ public abstract class AbstractCachingConfiguration implements ImportAware {
 	/**
 	 * Extract the configuration from the nominated {@link CachingConfigurer}.
 	 */
-	protected void useCachingConfigurer(CachingConfigurer config) {
+	protected void useCachingConfigurer(@Nullable CachingConfigurer config) {
 		this.cacheManager = config.cacheManager();
 		this.cacheResolver = config.cacheResolver();
 		this.keyGenerator = config.keyGenerator();

spring-context/src/main/java/org/springframework/cache/concurrent/ConcurrentMapCache.java

@@ -137,7 +137,8 @@ public class ConcurrentMapCache extends AbstractValueAdaptingCache {
 
 	@SuppressWarnings("unchecked")
 	@Override
-	public <T> T get(Object key, Callable<T> valueLoader) {
+	@Nullable
+	public <T> T get(@Nullable Object key, Callable<T> valueLoader) {
 		if (this.store.containsKey(key)) {
 			return (T) get(key).get();
 		}
@@ -154,18 +155,19 @@ public class ConcurrentMapCache extends AbstractValueAdaptingCache {
 	}
 
 	@Override
-	public void put(Object key, Object value) {
+	public void put(@Nullable Object key, @Nullable Object value) {
 		this.store.put(key, toStoreValue(value));
 	}
 
 	@Override
-	public ValueWrapper putIfAbsent(Object key, Object value) {
+	@Nullable
+	public ValueWrapper putIfAbsent(@Nullable Object key, @Nullable Object value) {
 		Object existing = this.store.putIfAbsent(key, toStoreValue(value));
 		return toValueWrapper(existing);
 	}
 
 	@Override
-	public void evict(Object key) {
+	public void evict(@Nullable Object key) {
 		this.store.remove(key);
 	}
 
@@ -175,7 +177,7 @@ public class ConcurrentMapCache extends AbstractValueAdaptingCache {
 	}
 
 	@Override
-	protected Object toStoreValue(Object userValue) {
+	protected Object toStoreValue(@Nullable Object userValue) {
 		Object storeValue = super.toStoreValue(userValue);
 		if (this.serialization != null) {
 			try {
@@ -203,7 +205,7 @@ public class ConcurrentMapCache extends AbstractValueAdaptingCache {
 	}
 
 	@Override
-	protected Object fromStoreValue(Object storeValue) {
+	protected Object fromStoreValue(@Nullable Object storeValue) {
 		if (this.serialization != null) {
 			try {
 				return super.fromStoreValue(deserializeValue(storeValue));

spring-context/src/main/java/org/springframework/cache/concurrent/ConcurrentMapCacheManager.java

@@ -146,7 +146,7 @@ public class ConcurrentMapCacheManager implements CacheManager, BeanClassLoaderA
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		this.serialization = new SerializationDelegate(classLoader);
 		// Need to recreate all Cache instances with new ClassLoader in store-by-value mode...
 		if (isStoreByValue()) {

spring-context/src/main/java/org/springframework/cache/interceptor/AbstractCacheResolver.java

@@ -95,6 +95,6 @@ public abstract class AbstractCacheResolver implements CacheResolver, Initializi
 	 * @return the cache name(s) to resolve or {@code null} if no cache should be resolved
 	 */
 	@Nullable
-	protected abstract Collection<String> getCacheNames(CacheOperationInvocationContext<?> context);
+	protected abstract Collection<String> getCacheNames(@Nullable CacheOperationInvocationContext<?> context);
 
 }

spring-context/src/main/java/org/springframework/cache/interceptor/AbstractFallbackCacheOperationSource.java

@@ -83,7 +83,7 @@ public abstract class AbstractFallbackCacheOperationSource implements CacheOpera
 	 * is not cacheable
 	 */
 	@Override
-	public Collection<CacheOperation> getCacheOperations(Method method, Class<?> targetClass) {
+	public Collection<CacheOperation> getCacheOperations(Method method, @Nullable Class<?> targetClass) {
 		if (method.getDeclaringClass() == Object.class) {
 			return null;
 		}

spring-context/src/main/java/org/springframework/cache/interceptor/CacheOperationSourcePointcut.java

@@ -35,7 +35,7 @@ import org.springframework.util.ObjectUtils;
 abstract class CacheOperationSourcePointcut extends StaticMethodMatcherPointcut implements Serializable {
 
 	@Override
-	public boolean matches(Method method, Class<?> targetClass) {
+	public boolean matches(Method method, @Nullable Class<?> targetClass) {
 		CacheOperationSource cas = getCacheOperationSource();
 		return (cas != null && !CollectionUtils.isEmpty(cas.getCacheOperations(method, targetClass)));
 	}

spring-context/src/main/java/org/springframework/cache/interceptor/CompositeCacheOperationSource.java

@@ -21,6 +21,7 @@ import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Collection;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -54,7 +55,7 @@ public class CompositeCacheOperationSource implements CacheOperationSource, Seri
 	}
 
 	@Override
-	public Collection<CacheOperation> getCacheOperations(Method method, Class<?> targetClass) {
+	public Collection<CacheOperation> getCacheOperations(Method method, @Nullable Class<?> targetClass) {
 		Collection<CacheOperation> ops = null;
 
 		for (CacheOperationSource source : this.cacheOperationSources) {

spring-context/src/main/java/org/springframework/cache/interceptor/NameMatchCacheOperationSource.java

@@ -25,6 +25,7 @@ import java.util.Map;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.PatternMatchUtils;
 
@@ -76,7 +77,7 @@ public class NameMatchCacheOperationSource implements CacheOperationSource, Seri
 	}
 
 	@Override
-	public Collection<CacheOperation> getCacheOperations(Method method, Class<?> targetClass) {
+	public Collection<CacheOperation> getCacheOperations(Method method, @Nullable Class<?> targetClass) {
 		// look for direct name match
 		String methodName = method.getName();
 		Collection<CacheOperation> ops = this.nameMap.get(methodName);

spring-context/src/main/java/org/springframework/cache/interceptor/NamedCacheResolver.java

@@ -22,6 +22,7 @@ import java.util.Arrays;
 import java.util.Collection;
 
 import org.springframework.cache.CacheManager;
+import org.springframework.lang.Nullable;
 
 /**
  * A {@link CacheResolver} that forces the resolution to a configurable
@@ -50,7 +51,7 @@ public class NamedCacheResolver extends AbstractCacheResolver {
 	}
 
 	@Override
-	protected Collection<String> getCacheNames(CacheOperationInvocationContext<?> context) {
+	protected Collection<String> getCacheNames(@Nullable CacheOperationInvocationContext<?> context) {
 		return this.cacheNames;
 	}
 

spring-context/src/main/java/org/springframework/cache/interceptor/SimpleCacheResolver.java

@@ -20,6 +20,7 @@ import java.util.Collection;
 
 import org.springframework.cache.Cache;
 import org.springframework.cache.CacheManager;
+import org.springframework.lang.Nullable;
 
 /**
  * A simple {@link CacheResolver} that resolves the {@link Cache} instance(s)
@@ -40,7 +41,7 @@ public class SimpleCacheResolver extends AbstractCacheResolver {
 	}
 
 	@Override
-	protected Collection<String> getCacheNames(CacheOperationInvocationContext<?> context) {
+	protected Collection<String> getCacheNames(@Nullable CacheOperationInvocationContext<?> context) {
 		return context.getOperation().getCacheNames();
 	}
 

spring-context/src/main/java/org/springframework/cache/support/AbstractValueAdaptingCache.java

@@ -53,14 +53,16 @@ public abstract class AbstractValueAdaptingCache implements Cache {
 	}
 
 	@Override
-	public ValueWrapper get(Object key) {
+	@Nullable
+	public ValueWrapper get(@Nullable Object key) {
 		Object value = lookup(key);
 		return toValueWrapper(value);
 	}
 
 	@Override
 	@SuppressWarnings("unchecked")
-	public <T> T get(Object key, Class<T> type) {
+	@Nullable
+	public <T> T get(@Nullable Object key, Class<T> type) {
 		Object value = fromStoreValue(lookup(key));
 		if (value != null && type != null && !type.isInstance(value)) {
 			throw new IllegalStateException("Cached value is not of required type [" + type.getName() + "]: " + value);
@@ -115,6 +117,7 @@ public abstract class AbstractValueAdaptingCache implements Cache {
 	 * @param storeValue the original value
 	 * @return the wrapped value
 	 */
+	@Nullable
 	protected Cache.ValueWrapper toValueWrapper(Object storeValue) {
 		return (storeValue != null ? new SimpleValueWrapper(fromStoreValue(storeValue)) : null);
 	}

spring-context/src/main/java/org/springframework/cache/support/NoOpCache.java

@@ -19,6 +19,7 @@ package org.springframework.cache.support;
 import java.util.concurrent.Callable;
 
 import org.springframework.cache.Cache;
+import org.springframework.lang.Nullable;
 
 /**
  * A no operation {@link Cache} implementation suitable
@@ -47,21 +48,21 @@ public class NoOpCache implements Cache {
 	}
 
 	@Override
-	public void evict(Object key) {
+	public void evict(@Nullable Object key) {
 	}
 
 	@Override
-	public ValueWrapper get(Object key) {
+	public ValueWrapper get(@Nullable Object key) {
 		return null;
 	}
 
 	@Override
-	public <T> T get(Object key, Class<T> type) {
+	public <T> T get(@Nullable Object key, Class<T> type) {
 		return null;
 	}
 
 	@Override
-	public <T> T get(Object key, Callable<T> valueLoader) {
+	public <T> T get(@Nullable Object key, Callable<T> valueLoader) {
 		try {
 			return valueLoader.call();
 		}
@@ -81,11 +82,12 @@ public class NoOpCache implements Cache {
 	}
 
 	@Override
-	public void put(Object key, Object value) {
+	public void put(@Nullable Object key, @Nullable Object value) {
 	}
 
 	@Override
-	public ValueWrapper putIfAbsent(Object key, Object value) {
+	@Nullable
+	public ValueWrapper putIfAbsent(@Nullable Object key, @Nullable Object value) {
 		return null;
 	}
 

spring-context/src/main/java/org/springframework/context/annotation/AnnotationConfigApplicationContext.java

@@ -214,7 +214,7 @@ public class AnnotationConfigApplicationContext extends GenericApplicationContex
 	}
 
 	@Override
-	public <T> void registerBean(String beanName, Class<T> beanClass, Supplier<T> supplier,
+	public <T> void registerBean(@Nullable String beanName, @Nullable Class<T> beanClass, Supplier<T> supplier,
 			BeanDefinitionCustomizer... customizers) {
 
 		this.reader.doRegisterBean(beanClass, supplier, beanName, null, customizers);

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassPostProcessor.java

@@ -61,6 +61,7 @@ import org.springframework.core.io.ResourceLoader;
 import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
 import org.springframework.core.type.classreading.MetadataReaderFactory;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 
@@ -201,7 +202,7 @@ public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPo
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader beanClassLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader beanClassLoader) {
 		this.beanClassLoader = beanClassLoader;
 		if (!this.setMetadataReaderFactoryCalled) {
 			this.metadataReaderFactory = new CachingMetadataReaderFactory(beanClassLoader);

spring-context/src/main/java/org/springframework/context/annotation/LoadTimeWeavingConfiguration.java

@@ -26,6 +26,7 @@ import org.springframework.context.weaving.DefaultContextLoadTimeWeaver;
 import org.springframework.core.annotation.AnnotationAttributes;
 import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.instrument.classloading.LoadTimeWeaver;
+import org.springframework.lang.Nullable;
 
 /**
  * {@code @Configuration} class that registers a {@link LoadTimeWeaver} bean.
@@ -64,7 +65,7 @@ public class LoadTimeWeavingConfiguration implements ImportAware, BeanClassLoade
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader beanClassLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader beanClassLoader) {
 		this.beanClassLoader = beanClassLoader;
 	}
 

spring-context/src/main/java/org/springframework/context/config/MBeanExportBeanDefinitionParser.java

@@ -25,6 +25,7 @@ import org.springframework.beans.factory.xml.AbstractBeanDefinitionParser;
 import org.springframework.beans.factory.xml.ParserContext;
 import org.springframework.jmx.export.annotation.AnnotationMBeanExporter;
 import org.springframework.jmx.support.RegistrationPolicy;
+import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 
 /**
@@ -60,7 +61,7 @@ class MBeanExportBeanDefinitionParser extends AbstractBeanDefinitionParser {
 	}
 
 	@Override
-	protected AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext) {
+	protected AbstractBeanDefinition parseInternal(@Nullable Element element, @Nullable ParserContext parserContext) {
 		BeanDefinitionBuilder builder = BeanDefinitionBuilder.rootBeanDefinition(AnnotationMBeanExporter.class);
 
 		// Mark as infrastructure bean and attach source location.

spring-context/src/main/java/org/springframework/context/config/MBeanServerBeanDefinitionParser.java

@@ -63,7 +63,7 @@ class MBeanServerBeanDefinitionParser extends AbstractBeanDefinitionParser {
 	}
 
 	@Override
-	protected AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext) {
+	protected AbstractBeanDefinition parseInternal(@Nullable Element element, @Nullable ParserContext parserContext) {
 		String agentId = element.getAttribute(AGENT_ID_ATTRIBUTE);
 		if (StringUtils.hasText(agentId)) {
 			RootBeanDefinition bd = new RootBeanDefinition(MBeanServerFactoryBean.class);

spring-context/src/main/java/org/springframework/context/event/AbstractApplicationEventMulticaster.java

@@ -33,6 +33,7 @@ import org.springframework.context.ApplicationEvent;
 import org.springframework.context.ApplicationListener;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
 
@@ -71,7 +72,7 @@ public abstract class AbstractApplicationEventMulticaster
 
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		this.beanClassLoader = classLoader;
 	}
 

spring-context/src/main/java/org/springframework/context/event/SimpleApplicationEventMulticaster.java

@@ -25,6 +25,7 @@ import org.springframework.beans.factory.BeanFactory;
 import org.springframework.context.ApplicationEvent;
 import org.springframework.context.ApplicationListener;
 import org.springframework.core.ResolvableType;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ErrorHandler;
 
 /**
@@ -123,7 +124,7 @@ public class SimpleApplicationEventMulticaster extends AbstractApplicationEventM
 	}
 
 	@Override
-	public void multicastEvent(final ApplicationEvent event, ResolvableType eventType) {
+	public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) {
 		ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));
 		for (final ApplicationListener<?> listener : getApplicationListeners(event, type)) {
 			Executor executor = getTaskExecutor();

spring-context/src/main/java/org/springframework/context/support/AbstractApplicationContext.java

@@ -76,6 +76,7 @@ import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
 import org.springframework.core.io.support.ResourcePatternResolver;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.ReflectionUtils;
@@ -461,7 +462,7 @@ public abstract class AbstractApplicationContext extends DefaultResourceLoader
 	 * @see ConfigurableEnvironment#merge(ConfigurableEnvironment)
 	 */
 	@Override
-	public void setParent(ApplicationContext parent) {
+	public void setParent(@Nullable ApplicationContext parent) {
 		this.parent = parent;
 		if (parent != null) {
 			Environment parentEnvironment = parent.getEnvironment();
@@ -844,7 +845,7 @@ public abstract class AbstractApplicationContext extends DefaultResourceLoader
 		if (!beanFactory.hasEmbeddedValueResolver()) {
 			beanFactory.addEmbeddedValueResolver(new StringValueResolver() {
 				@Override
-				public String resolveStringValue(String strVal) {
+				public String resolveStringValue(@Nullable String strVal) {
 					return getEnvironment().resolvePlaceholders(strVal);
 				}
 			});
@@ -1081,7 +1082,7 @@ public abstract class AbstractApplicationContext extends DefaultResourceLoader
 	}
 
 	@Override
-	public <T> T getBean(String name, Class<T> requiredType) throws BeansException {
+	public <T> T getBean(String name, @Nullable Class<T> requiredType) throws BeansException {
 		assertBeanFactoryActive();
 		return getBeanFactory().getBean(name, requiredType);
 	}
@@ -1165,31 +1166,31 @@ public abstract class AbstractApplicationContext extends DefaultResourceLoader
 	}
 
 	@Override
-	public String[] getBeanNamesForType(ResolvableType type) {
+	public String[] getBeanNamesForType(@Nullable ResolvableType type) {
 		assertBeanFactoryActive();
 		return getBeanFactory().getBeanNamesForType(type);
 	}
 
 	@Override
-	public String[] getBeanNamesForType(Class<?> type) {
+	public String[] getBeanNamesForType(@Nullable Class<?> type) {
 		assertBeanFactoryActive();
 		return getBeanFactory().getBeanNamesForType(type);
 	}
 
 	@Override
-	public String[] getBeanNamesForType(Class<?> type, boolean includeNonSingletons, boolean allowEagerInit) {
+	public String[] getBeanNamesForType(@Nullable Class<?> type, boolean includeNonSingletons, boolean allowEagerInit) {
 		assertBeanFactoryActive();
 		return getBeanFactory().getBeanNamesForType(type, includeNonSingletons, allowEagerInit);
 	}
 
 	@Override
-	public <T> Map<String, T> getBeansOfType(Class<T> type) throws BeansException {
+	public <T> Map<String, T> getBeansOfType(@Nullable Class<T> type) throws BeansException {
 		assertBeanFactoryActive();
 		return getBeanFactory().getBeansOfType(type);
 	}
 
 	@Override
-	public <T> Map<String, T> getBeansOfType(Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
+	public <T> Map<String, T> getBeansOfType(@Nullable Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
 			throws BeansException {
 
 		assertBeanFactoryActive();
@@ -1249,12 +1250,12 @@ public abstract class AbstractApplicationContext extends DefaultResourceLoader
 	//---------------------------------------------------------------------
 
 	@Override
-	public String getMessage(String code, Object args[], String defaultMessage, Locale locale) {
+	public String getMessage(String code, @Nullable Object args[], String defaultMessage, Locale locale) {
 		return getMessageSource().getMessage(code, args, defaultMessage, locale);
 	}
 
 	@Override
-	public String getMessage(String code, Object args[], Locale locale) throws NoSuchMessageException {
+	public String getMessage(String code, @Nullable Object args[], Locale locale) throws NoSuchMessageException {
 		return getMessageSource().getMessage(code, args, locale);
 	}
 

spring-context/src/main/java/org/springframework/context/support/AbstractMessageSource.java

@@ -72,7 +72,7 @@ public abstract class AbstractMessageSource extends MessageSourceSupport impleme
 
 
 	@Override
-	public void setParentMessageSource(MessageSource parent) {
+	public void setParentMessageSource(@Nullable MessageSource parent) {
 		this.parentMessageSource = parent;
 	}
 
@@ -134,7 +134,7 @@ public abstract class AbstractMessageSource extends MessageSourceSupport impleme
 
 
 	@Override
-	public final String getMessage(String code, Object[] args, String defaultMessage, Locale locale) {
+	public final String getMessage(String code, @Nullable Object[] args, String defaultMessage, Locale locale) {
 		String msg = getMessageInternal(code, args, locale);
 		if (msg != null) {
 			return msg;
@@ -149,7 +149,7 @@ public abstract class AbstractMessageSource extends MessageSourceSupport impleme
 	}
 
 	@Override
-	public final String getMessage(String code, Object[] args, Locale locale) throws NoSuchMessageException {
+	public final String getMessage(String code, @Nullable Object[] args, Locale locale) throws NoSuchMessageException {
 		String msg = getMessageInternal(code, args, locale);
 		if (msg != null) {
 			return msg;

spring-context/src/main/java/org/springframework/context/support/DelegatingMessageSource.java

@@ -22,6 +22,7 @@ import org.springframework.context.HierarchicalMessageSource;
 import org.springframework.context.MessageSource;
 import org.springframework.context.MessageSourceResolvable;
 import org.springframework.context.NoSuchMessageException;
+import org.springframework.lang.Nullable;
 
 /**
  * Empty {@link MessageSource} that delegates all calls to the parent MessageSource.
@@ -40,7 +41,7 @@ public class DelegatingMessageSource extends MessageSourceSupport implements Hie
 
 
 	@Override
-	public void setParentMessageSource(MessageSource parent) {
+	public void setParentMessageSource(@Nullable MessageSource parent) {
 		this.parentMessageSource = parent;
 	}
 
@@ -51,7 +52,7 @@ public class DelegatingMessageSource extends MessageSourceSupport implements Hie
 
 
 	@Override
-	public String getMessage(String code, Object[] args, String defaultMessage, Locale locale) {
+	public String getMessage(String code, @Nullable Object[] args, String defaultMessage, Locale locale) {
 		if (this.parentMessageSource != null) {
 			return this.parentMessageSource.getMessage(code, args, defaultMessage, locale);
 		}
@@ -61,7 +62,7 @@ public class DelegatingMessageSource extends MessageSourceSupport implements Hie
 	}
 
 	@Override
-	public String getMessage(String code, Object[] args, Locale locale) throws NoSuchMessageException {
+	public String getMessage(String code, @Nullable Object[] args, Locale locale) throws NoSuchMessageException {
 		if (this.parentMessageSource != null) {
 			return this.parentMessageSource.getMessage(code, args, locale);
 		}

spring-context/src/main/java/org/springframework/context/support/GenericApplicationContext.java

@@ -150,7 +150,7 @@ public class GenericApplicationContext extends AbstractApplicationContext implem
 	 * @see org.springframework.beans.factory.config.ConfigurableBeanFactory#setParentBeanFactory
 	 */
 	@Override
-	public void setParent(ApplicationContext parent) {
+	public void setParent(@Nullable ApplicationContext parent) {
 		super.setParent(parent);
 		this.beanFactory.setParentBeanFactory(getInternalParentBeanFactory());
 	}
@@ -238,7 +238,7 @@ public class GenericApplicationContext extends AbstractApplicationContext implem
 	}
 
 	@Override
-	public void setClassLoader(ClassLoader classLoader) {
+	public void setClassLoader(@Nullable ClassLoader classLoader) {
 		super.setClassLoader(classLoader);
 		this.customClassLoader = true;
 	}

spring-context/src/main/java/org/springframework/context/support/PropertySourcesPlaceholderConfigurer.java

@@ -31,6 +31,7 @@ import org.springframework.core.env.PropertiesPropertySource;
 import org.springframework.core.env.PropertySource;
 import org.springframework.core.env.PropertySources;
 import org.springframework.core.env.PropertySourcesPropertyResolver;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringValueResolver;
 
@@ -166,7 +167,8 @@ public class PropertySourcesPlaceholderConfigurer extends PlaceholderConfigurerS
 
 		StringValueResolver valueResolver = new StringValueResolver() {
 			@Override
-			public String resolveStringValue(String strVal) {
+			@Nullable
+			public String resolveStringValue(@Nullable String strVal) {
 				String resolved = (ignoreUnresolvablePlaceholders ?
 						propertyResolver.resolvePlaceholders(strVal) :
 						propertyResolver.resolveRequiredPlaceholders(strVal));

spring-context/src/main/java/org/springframework/context/support/ResourceBundleMessageSource.java

@@ -114,7 +114,7 @@ public class ResourceBundleMessageSource extends AbstractResourceBasedMessageSou
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		this.beanClassLoader = (classLoader != null ? classLoader : ClassUtils.getDefaultClassLoader());
 	}
 

spring-context/src/main/java/org/springframework/context/weaving/AspectJWeavingEnabler.java

@@ -53,7 +53,7 @@ public class AspectJWeavingEnabler
 
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		this.beanClassLoader = classLoader;
 	}
 

spring-context/src/main/java/org/springframework/context/weaving/DefaultContextLoadTimeWeaver.java

@@ -69,7 +69,7 @@ public class DefaultContextLoadTimeWeaver implements LoadTimeWeaver, BeanClassLo
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		LoadTimeWeaver serverSpecificLoadTimeWeaver = createServerSpecificLoadTimeWeaver(classLoader);
 		if (serverSpecificLoadTimeWeaver != null) {
 			if (logger.isInfoEnabled()) {

spring-context/src/main/java/org/springframework/ejb/access/LocalStatelessSessionProxyFactoryBean.java

@@ -21,6 +21,7 @@ import javax.naming.NamingException;
 import org.springframework.aop.framework.ProxyFactory;
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.beans.factory.FactoryBean;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 
 /**
@@ -78,7 +79,7 @@ public class LocalStatelessSessionProxyFactoryBean extends LocalSlsbInvokerInter
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		this.beanClassLoader = classLoader;
 	}
 

spring-context/src/main/java/org/springframework/ejb/access/SimpleRemoteStatelessSessionProxyFactoryBean.java

@@ -21,6 +21,7 @@ import javax.naming.NamingException;
 import org.springframework.aop.framework.ProxyFactory;
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.beans.factory.FactoryBean;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 
 /**
@@ -92,7 +93,7 @@ public class SimpleRemoteStatelessSessionProxyFactoryBean extends SimpleRemoteSl
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		this.beanClassLoader = classLoader;
 	}
 

spring-context/src/main/java/org/springframework/format/support/FormattingConversionService.java

@@ -36,6 +36,7 @@ import org.springframework.format.Formatter;
 import org.springframework.format.FormatterRegistry;
 import org.springframework.format.Parser;
 import org.springframework.format.Printer;
+import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 import org.springframework.util.StringValueResolver;
 
@@ -145,7 +146,7 @@ public class FormattingConversionService extends GenericConversionService
 
 		@Override
 		@SuppressWarnings("unchecked")
-		public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		public Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
 			if (source == null) {
 				return "";
 			}
@@ -186,7 +187,7 @@ public class FormattingConversionService extends GenericConversionService
 		}
 
 		@Override
-		public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		public Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
 			String text = (String) source;
 			if (!StringUtils.hasText(text)) {
 				return null;
@@ -247,7 +248,7 @@ public class FormattingConversionService extends GenericConversionService
 
 		@Override
 		@SuppressWarnings("unchecked")
-		public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		public Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
 			Annotation ann = sourceType.getAnnotation(this.annotationType);
 			if (ann == null) {
 				throw new IllegalStateException(
@@ -301,7 +302,7 @@ public class FormattingConversionService extends GenericConversionService
 
 		@Override
 		@SuppressWarnings("unchecked")
-		public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+		public Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
 			Annotation ann = targetType.getAnnotation(this.annotationType);
 			if (ann == null) {
 				throw new IllegalStateException(

spring-context/src/main/java/org/springframework/jmx/access/MBeanClientInterceptor.java

@@ -231,7 +231,7 @@ public class MBeanClientInterceptor
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader beanClassLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader beanClassLoader) {
 		this.beanClassLoader = beanClassLoader;
 	}
 

spring-context/src/main/java/org/springframework/jmx/access/MBeanProxyFactoryBean.java

@@ -21,6 +21,7 @@ import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.beans.factory.FactoryBean;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.jmx.MBeanServerNotFoundException;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 
 /**
@@ -67,7 +68,7 @@ public class MBeanProxyFactoryBean extends MBeanClientInterceptor
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		this.beanClassLoader = classLoader;
 	}
 

spring-context/src/main/java/org/springframework/jmx/export/MBeanExporter.java

@@ -386,7 +386,7 @@ public class MBeanExporter extends MBeanRegistrationSupport implements MBeanExpo
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader classLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader classLoader) {
 		this.beanClassLoader = classLoader;
 	}
 

spring-context/src/main/java/org/springframework/jmx/export/assembler/InterfaceBasedMBeanInfoAssembler.java

@@ -26,6 +26,7 @@ import java.util.Properties;
 
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.beans.factory.InitializingBean;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.StringUtils;
 
@@ -110,7 +111,7 @@ public class InterfaceBasedMBeanInfoAssembler extends AbstractConfigurableMBeanI
 	}
 
 	@Override
-	public void setBeanClassLoader(ClassLoader beanClassLoader) {
+	public void setBeanClassLoader(@Nullable ClassLoader beanClassLoader) {
 		this.beanClassLoader = beanClassLoader;
 	}